1. Field of the Invention
The present invention relates to an H-bridge micro inverter grid-connected device which belongs to the technical field of electrical engineering.
2. The Prior Arts
The common existing inverter grid-connected devices operate in high power. Many photovoltaic panels are needed to be connected in series in several groups, and then, different series photovoltaic panel modules are connected in parallel to form a photovoltaic array. DC generated by the solar panel array converges to the inverter beside the solar panel. In such photovoltaic system, the solar panel is formed by connecting multiple series photovoltaic panel modules in parallel. Like festival lights, if a battery in the series circuit does not work, the whole battery pack will fail. In addition, the situation can also occur when a partial shadow or particles shade the photovoltaic system. The result is that power generating capacity of solar energy decreases by 50% if only 10% of the solar photovoltaic system is shaded. The situation above is caused by unreasonable structure of the existing photovoltaic systems, which affects reliability, costs and efficiency of inversion. The reason is that multi-photovoltaic panel cascaded convergence inversion causes the fact that failure of some solar photovoltaic panels affects the whole photovoltaic power generation system. If the photovoltaic power generation structure above is not used, one method of the common existing inverters is that inversion to low-voltage AC is performed firstly, and then, the low-voltage AC is transformed by a self-adjusting power frequency transformer to AC which conforms to grid-connected requirements. However, the method requires high performance of transformers, and transformers are expensive and huge to users. Still, although the inverter circuit is simplified, the transformers have poor economical efficiency and reliability. Another common method is that the voltage of the current is boosted to a certain range by the DC/DC boost circuit firstly, and then, the current is inverted to AC of power frequency which conforms to grid-connected requirements. The common DC/DC method of high reliability and high stability needs many full-control switches and power diodes to design the whole solar inverter grid-connected device, so the method has the disadvantages of high costs, complex control and difficult system maintenance.